Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.62	10.708%	$233.1732	$233.17	$233.15	$233.20
Purchase #2	$111.69	10.237%	$123.1237	$123.12	$123.10	$123.10
Purchase #3	$175.95	4.439%	$183.7604	$183.76	$183.75	$183.80
Purchase #4	$24.85	5.154%	$26.1308	$26.13	$26.15	$26.10
Purchase #5	$222.91	13.727%	$253.5089	$253.51	$253.50	$253.50
Purchase #6	$100.96	9.823%	$110.8773	$110.88	$110.90	$110.90
Purchase #7	$95.83	8.862%	$104.3225	$104.32	$104.30	$104.30
7 purchase totals =	$942.81		$1,034.8968	$1,034.89	$1,034.85	$1,034.90